92 TRANSPORTATION RESEARCH R ECORD 1258

Performance Evaluation of a Movable Concrete Barrier

DORAN L. GLAUZ

A series of crash tests and operational demon lration of a precast movable concrete barrier (MCB) were performed. Four orash test of the M B showed rhat it can successfully redirecl both light and heavy passenger car at variou angles of impact. The era h tests involved two large cars weighing 4,370 lb and 4,300 lb traveling 59.3 and 59.4 mph and striking at 24 degree · and 16 degrees, respectiv ly; and two small cars weighing 2,000 lb and J ,895 lb , Lraveling 57.7 and 58.6 mph , an I striking at lsYz degrees and 20Y2 degrees, respectively. The crash te t ati. fled tbe requirement for tru tural adequacy and oc upam risk in NCHRP Report 230. Vehicle trajectory rcquir ments were not satisfied because of large exit angles. The demonstration con­si ·ted of (a) a ransfer vehicle strnightening a deflected barrier after the last crash test· (b) a transfer vehicle Iran porting, assem­bling, and transferring a barrier n a 1,400-ft r, dius with a 12 percent cross-slope · (c) a traJlSfer vehicle transferring a barrier on a 4 to 5 percent I ngi tudinal grade ; and (d) manual movement of the barrier to adjust minor misalignmenrs. The M 13 move IHlt:rally under impacr . The lateral movement is related to impact severity. Two equation are presented to predict lateral movement as a function of impact severity.

Traffic congestion has increased rapidly in recent years. At many highway and bridge locations there has not been room to add lanes or funds have been insufficient. At those locations where traffic is heavy in one direction in the morning and heavy in the opposite direction in the evening, a need has developed for a median barrier that can be moved easily from one lane boundary to another. With a movable barrier it would be possible to adjust the number of lanes available to peak traffic daily, while maintaining a positive barrier between opposing traffic lanes. The California Department of Trans­portation (Caltrans) has a pressing need for such a barrier on the Coronado Bridge in San Diego. The relocatable pylons used there now do nothing to retain out-of-control vehicles, and there have been severe head-on collisions. There are other locations where a movable barrier could be used to advantage. These include locations where a permanent system is needed and al o construction and maintenance locations where a mobile barrier is needed that would provide greater protection to motorists and workers. Over the years several systems have been proposed to Caltrans. These systems have required an extensive and complicated mechanical installation within the roadbed, introducing a potential maintenance headache and precluding them from temporary use, or have demonstrated inferior performance as a barrier.

Transportation Laboratory, California Department of Tran porla­tion, 5900 Folsom Blvd., P.O. Box 19128, aernmcnto, Calif. 95819.

DESCRIPTION OF BARRIER AND TRANSFER VEHICLE

A barrier that meets the criterion of simplicity and requires no roadbed modification has been developed. This barrier was conceived, developed, and tested in response to a con­tinuing demand for a movable barrier from the United States and other countries. The Quickchange Movable Concrete Barrier System was invented by Ouick- tee! Engine ring Pty, Ltd., of Botany, New S uth Wal.es, Australia . Barrier Sys­tems, Inc. (BSI) of Sau alito, alif rnia , is the North Amer­ican licensee for the system. Hereafter this system will be referred to as a movable concrete barrier (MCB).

The MCB is a segmented concrete barrier formed similar to a Configuration F-shape modified with a narrowed neck and a T-shaped top (Figure 1). Tb seg111e1 t. are .>.2 ft (1 m) long 2 ft (609 mm) wide at the base, and 32 in. (812 mm) high . T hey nre joined together by a pin-and-link hinge.

The MCB is moved from one traffic lane line to another with a transfer vehicle (Figure 2) . The vehicle is a mobile steel framework, which may be either self-propelled or towed, with an S- haped conveyor assembly mounted n it. lose ly spaced urethane conveyor wl1eeJ ride under the flange of the T- ·hape of the tcm (Figure ). Tbe segments a re lifted off the pavement by tl:e wheels, guided along the S-shaped conveyor to the new lane position, and lowered back down to the pavement. The barrier segment · remain pinned together during the transfer operation. A the vehicle move fon ard, the barrier i transferred from left to right (when u ed as a median barrier), minimizing the exposure of the transfer vehicle to traffic in both directions (Figure 2).

SCOPE OF RESEARCH

A series of crash tests and operational demonstrations of the MCB were performed. Two crash tests indicated a deficiency in the original design. After modification by the manufac­turer, four additional tests demonstratecl successful redirec­tion of large and small cars. Four operational demonstrations indicated the maneuverability and maintainability of the MCB.

BARRIER DESIGN

Two tests were conducted on two versions of the original Australian design and are described in the full report (1). The tests were at impact angles of 15 degrees and 25 degrees with heavy vehicles at 60 mph (27 m/sec). The lateral deflections

G/auz

3.28'

~

=

FIGURE 1 End view and elevation of MCB.

TRANSFER VEHICLE

I I

LOW TRAFFIC PERIOD TRANSFER

t=

~

FIGURE 2 Transfer vehicle moves barrier one full lane width.

were 4.56 and 5.77 ft (1.4 and 1.8 m) tor the two tests. The strength of the stem proved to be inadequate. Because this barrier was anticipated for use on a permanent installation, the lateral deflection was considered excessive.

The manufacturer, BSI, undertook a testing and develop­ment program to design a stronger stem and to determine what factors are important to lateral deflection . The stem was strengthened by thickening the narrow neck section, increas-

93

ing it from 5Ys in. (130 mm) to 8Ys in. (206 mm) and increasing the reinforcement from 6 x 6- W5 x WS welded wire fabric to two No. 4 reinforcing bars plus 4 x 4-W4 x W4 welded wire fabric. In addition, the wire fabric was bent outward into the top flange (Figure 4).

The method devised to limit the lateral deflection was to reduce the longitudinal clearance in the hinge assembly (Fig­ure 5). The original design had a ± V2 in . (12.7 mm) clearance to allow for barrier lengthening and shortening in changing radii and expansion joints on bridges. This clearance was reducted to ± 3/ 16 in . (4.8 mm). By reducing the clearance , more barrier segments (more mass) must be mobilized to effect a unit of lateral movement; thus more energy would be required per unit.

TEST RES UL TS

Test 443 (4,370 lb, 59.3 mph, 24 degrees)

The left front bumper of the test vehicle struck the 100-seg­ment barrier at the midpoint of Segment 62 at 59.3 mph (26.5 m/sec) and an angle of 24 degrees. The length of vehicle contact with the barrier was about 39 ft (12 m), from Segments 62 to 74. The car was smoothly redirected and lost contact with the barrier at an exit angle of 143/4 degrees. The car

FIGURE 3 Barrier is lifted by conveyor wheels under the MCB flange.

Test 441 , 442 Barrier Test 443 thru 446 Barrier

FIGURE 4 Changes from Australian barrier design.

94

1:1/2" or 3/16"

Cross Section

-E ,

/

L r $) '"

Plan View FIGURE 5 Simplified hinge detail.

experienced a maximum roll of -1QV4 degrees. The maximum rise of the car was 4 in. (100 mm) 0. 73 sec after impact, measured at the right rear corner of the roof. Figure 6 shows sequential photographs and a trajectory diagram.

The trajectory of the car after impact was back toward the line of the barrier. A second impact with the barrier occurred at Segment 93. The car came to rest about 30 ft (9 .1 m) beyond the downstream end of the barrier and approximately in line with its face (Figure 7).

The barrier was displaced laterally along a distance of about 66 ft (20 m) (Segments 54 through 75) . The maximum lateral displacement was 3.74 ft (1.3 m) at Segment 66 (Figure 8). There was longitudinal movement in the barrier from Seg­ments 22 to 100. The maximum longitudinal displacement in the downstream direction was 0.5 ft (140 mm) at Segment 54. The maximum longitudinal displacement in the upstream direction was 0.15 ft (45 mm).

Test 444 (2,000 lb, 57 .7 mph, 151/z degree~)

The left front bumper of the test vehicle struck the 100-seg­ment barrier at the midpoint of Segment 48 at 57.7 mph (25.8 m/sec) and an angle of 151/z degrees. The length of vehicle contact with the barrier was about 16 ft (5 m), from Segments 48 to 52. The car was smoothly redirected and lost contact with the barrier at an exit angle of 10% degrees. The car experienced a maximum roll of -14V2 degrees and a pitch of + 10% degrees. The maximum rise of the car was 17 in. (430 mm) 0.36 sec after impact, measured on the right rear tire. Figure 9 shows sequential photographs and a trajectory diagram.

The trajectory of the car after impact was away from the barrier. The car came to rest off the paved area about 15 ft (4.6 m) beyond the downstream end of the barrier and 60 ft (18 m) from its face (Figure 10).

The barrier was displaced laterally along a distance of about 30 ft (9 m) (Segments 47 through 55) (Figure 11). The max­imum lateral displacement was 1.78 ft (542 mm) at Segment

TRANSPORTATION RESEARCH RECORD 1258

51. There was longitudinal movement in the barrier from Segrn ' nt · 36 to 65. T he maximum longitudina l di. placement in the downstream direction was 0.1 fl (30 mm) at gment 47. The maximum longitudinal displacement in the upstream dire lion was 0. 1 ft (3J. mm) at cgment 55.

Test 445 (4,300 lb, 59.4 mph, 16 degrees)

The left front bumper of Lhe test vehicle struck the 100-seg­ment barrier at the midpoint of egment 52 at 59.4 mph (26.6 m/sec) and an angle of 16 degrees. The length of vehicle contact with the barrie r was about 33 ft (10 m), from Segments 52 to 61. The car was smoothly red irected and lost con tact with the barrier at an exit angle of 16'h degrees. The car experienced a maximum roll of + 6\1.1 degrees and a pitcb of +5.Ys degrees. The max imum rise of th car was 19 in. (490 mm) 0.54 sec after impact , measured on the right rear bumper. Figure 12 hows equence photographs and a trajectory diagram.

The trajectory of the car after impact was away from the barrier. The car came to rest off the paved area at the toe of an earth berm about 79 ft (24 m) beyond the downstream end of the barrier and 41 ft (12.5 mm) from its face (Figure 13).

The barrier was displaced laterally along a distance f about 59 ft (18 m) (Segments 47 through 65). The maximum lateral displacement was 2.85 ft (870 mm) at Segment 59 (Pigure 14). There was longitudinal moveme nt in the barrier from Seg­ments 26 to 81. The maximum longitudinal displacement in the downstream direction was 0.4 ft (110 mm) at Segment 58. The maximum longitudi11al displacement in the upstream direction was 0.1 ft (34 mm) at Segment 70.

Test 446 (1,895 lb, 58.6 mph, 201/2 degrees)

The left front bumper of the test vehicle struck the 100-seg­ment barrier at Segment 55 at 58 .6 mph (26.2 m/sec) and an angle of 20Yz degrees. The length of vehicle contact with the barrier was about 20 ft (6 m) , from Segments 55 to 60. The car was smoothly redirected and lost contact with the barrier at an exit angle of 19Yz degrees. The car experienced a max­imum roll of -15 degrees and a pitch of + 12V2 degrees. The maximum rise of the car was 30 in. (760 mm) 0.44 sec after impact, measured on the right rear bumper. Figure 15 shows sequence photographs and a trajectory diagram.

The trajectory of the car after impact was away from the barrier. The car came to rest about even with the downstream end of the barrier 37 ft (11 m) away from its face (Figure 16).

The barrier was displaced laterally along a distance of about 42 ft (13 m) (Segments 52 through 64). The maximum lateral displacement was 2.24 ft (684 mm) at Segment 59(Figure17). There was longitudinal movement from Segments 37 to 84. The maximum longitudinal displacement in the downstream direction was 0.15 ft (48 mm) at Segment 55. The maximum longitudinal displacement in the upstream direction was 0.2 ft (54 mm) at Segment 64.

DISCUSSION OF TEST RESULTS

In Tests 443 through 446 the MCB demonstrated its ability to retain ;mcl redirect a vehicle under a variety of impact

Impact+ 0.014 s I+ 0.074 s I + 0.204 s

I+ 0.674 s I + 1.32 s I+ 1.68 s

Displaced ~ Displaced Segments _ - -

Final Position Segments• I .... -£8:!.e_ath f--66'±--I - -Oflhe car f--=28' ,;""' 14l'4° -........ I ---1-- 24"

~---/--, . ----- f 2.3' 3.74~ .. ::::~ -:.--1 .... •'-----~8(1------:~1 L30' .. 328'----------------=..I-

1'=0.3048 m NOTTO SCALE

Test Barrier: Type: Movable Concrete Barrier (Simple Hinge Connections with Reduced Clearance) Length:

Test Date: TestVehlcle:

Model: Inertial Mass: Impact Velocity: Impact; Exit Angle :

Test Dummy: Type: Weight I Restraint: Position:

Test Data:

328 ft (100 m) - 100 segments November 18, 1987

1982 Olds Station Wagon 4370 lb (1982 kg) 59.3 mph (26.5 mis) 24 deg; 14314 deg

Part 572, 50th Percentile Male 165 lb (75 kg)/ none Driver's seat

Occupant Impact Velocity (long): 27.0 fps. (8.2 m/s) Max 50 ms Avg Accel: HIC I TAD I VDI: Max Roll;Pitch;Yaw : Barrier Displacement: Max Dynamic Deflection (film):

long -8.3 g, lat -7.7 g, vert -2.0 g 121 I LFQ6 / 11 LDEW2 -10114 deg; NA; NA 3.74 ft (1.14 m) at segment 66 4.10 ft (1.25m)

1"=0.0254 m

Barrier Damage: Minor scratches on 11 segments at the area of contact with test car

FIGURE 6 Summary of data for Test 443.

96

FIGURE 7 Car and barrier after impact, Test 443.

FIGURE 8 Deflected barrier after impact, Test 443.

TRANSPORTATION RESEARCH RECORD 1258

conditions. Vehicle rederection was smooth in all these tests. There was no tendency for the barrier to pocket or trap the vehicles. There was no evidence of any structural distress of the barrier segments. All four tests were performed on the same set of barrier segments without replacing any segments, welded hinge plates, or steel hinge pins. Segments were shifted after each test so fresh segments would be located in the main impact zone.

There was significant lateral displacement of the test barrier during each test (Table 1). The barrier displacement was closely related to impact severity (IS) . The data from these tests were statistically analyzed to obtain an equation for lateral displacement as a function of IS.

Two equations (Table 2) were found to fit the experimental data. These equations are represented in graphical form with the experimental data in Figure 18. The correlation is signif­icant at the 5 percent level (2, pp. 462-463). Data from other tests were also used in deriving these equations (1; E. F. Nordlin, unpublished data) .

For very small values, up to 3.8 ft-kips (5.2 kJ), no deflec­tion is predicted by Equation 1. Although the second equation approaches a zero displacement as IS approaches zero , it can be considered to evaluate to zero for IS less than 1 ft-kip (1.4 kJ).

For small impacts, up to 15 ft-kips (20 kJ), it is believed that Equation 1 understates the displacement that might be expected. Within this impact severity range, Equation 2 prob­ably gives a better value of lateral displacement . The reason why the lateral displacement is probably larger than that pre­dicted by Equation 1 lies in the action within the hinge during impact. In high-IS impacts, like those used to derive Equation 1, many of the barrier segments move. For each segment that moves , the entire longitudinal clearance in the hinge is taken up, effecting a lengthening of the barrier to allow lateral movement. During low-energy impacts many fewer segments are brought into the movement zone , down to the limiting case where only two segments move at all. In an impact when only two or three segments move , all the longitudinal clear­ance in the hinge may not be used, thus allowing movement with very low energy . .input.

In the range of 15 to 130 ft-kips (20 to 175 kJ) , the two equations give the same answer within the accuracy that can be expected from such an estimator. Caution must be exer­cised when using these equations to extrapolate beyond 100 ft-kips (135 kJ), because that is beyond the value of any data used to derive the equations. At some unknown value of impact severity some structural elements of the barrier may fail, thus invalidating any attempt at predicting defl ection.

Table 3 shows roll, pitch, and yaw values, maximum 50 msec average accelerations , occupant impact velocities , and rid down accelerations. For comparison, Tests 443 through 446 are included with data from previous tests on continuou concrete safety shaped barriers done by Caltrans.

Note that the magnitude of roll in Tests 443 through 446 is generally lower than in other tests of concrete safety shaped barriers. The amount of roll and pitch is low to moderate in all MCB tests. None of the test cars showed any indication of being close to rollover. Scuff and rub marks on the face of the barrier indicated that the projecting cap of the MCB restricted the climb of the car, thereby minimizing the roll angle.

Impact+ 0.054 s I+ 0.209 s I+ 0.401 s

I+ 0.591 s I+ 1.288 s I+ 2.322 s

~ ~nal Position

~ Th•Cat

r I''............. Displaced ~ ~ -----<2.ar_P~~---- Segments ----~

I ,., . ...,. ' . .. " lf"'':;;J::r.\;~:1::::.;;::)]i•'.'",~;;:· . ""'··-H- •

I 1.78'' 1- 158' :1 • 328' _ _ ___ _ _ ____ _ ;.,.

Test Barrier: 1'=0.3048 m NOTTO SCALE

Type: Movable Concrete Barrier (Simple Hinge Connections with Reduced Clearance) Length:

Test Date: TestVehlcle:

Model: Inertial Mass: Impact Velocity: Impact; Exit Angle :

Test Dummy: Type: Weight I Restraint: Position:

Test Data:

328 ft (100 m) - 100 segments December 18, 1987

1981 Honda Civic 2000 lb (907 kg) 57.7 mph (25.8 mis) 15112deg; 10114 deg

Part 572, 50th Percentile Male 165 lb (75 kg)/ none Driver's seat

Occupant Impact Velocity (long): 15.1 fps. (4.6 mis) long-4.6 g, lat - 6.7 g, vert 1.7 g Max 50 ms Avg Accel:

HIC /TAD I VDI: Max Roll;Pltch ;Yaw : Barrier Displacement: Max Dynamic Deflection (film) :

30 I LFQ4 I 12LDEE2 -14112 deg; 10114 deg; NA 1.78 ft (0.54 m) at segment 51 1.92 ft {0.58 m)

1"=0.0254 m

Barrier Damage : Minor scratches at the area of contact with test car

FIGURE 9 Summary of data for Test 444.

98

FIGURE 10 Car and barrier after impact, Test 444.

FIGURE 11 Deflected barrier after impact, Test 444.

The longitudinal occupant impact velocity in Test 444 (see Table 3) was below the NCH RP Report 2 0 (3) recommended maximum value and also smaller than in other Caltrans tests on permanent concrete median harriers. Although this was the only test required to meet Section F of the occupant risk requirements of NCHRP Report 230, the criterion was also met in Tests 443, 445, and 446.

In all four tests the exit angle exceeded 60 percent of the impact angle, the recommended limit in NCHRP Report 230, though only slightly in Tests 443 and 444 (Table 4). In Test 443 the velocity change also exceeded the recommended limit, 15 mph. In that test, the vehicle steered back toward the MCB and struck a second time. In Tests 444, 445, and 446 the vehicle speed change was 11 to 12 mph ( 4. 9 to 5 .3 m/sec) ,

TRANSPORTATION RESEARCH RECORD 1258

and the vehicles then crossed the traveled way and came to rest 40 to 60 ft (11 to 18 m) from the barrier face. The vehicles were disabled in all four tests and stopped 150 to 200 ft ( 45 to 62 m) from the impact point.

THE TRANSFER VEHICLE

The transfer vehicle is 49 ft (15 m) long and 8.2 ft (2 .5 m) wide and weighs 30 tons (27 000 kg) (Figure 19). It is self­powered; a 200-hp (150-kW) diesel engine powers a hydraulic drive and steering. Each wheel can be independently raised and lowered. A barrier can be transferred onto or off a curb up to 12 in. high. The lateral move of the barrier can be varied from 6 ft to 16 ft. Up to 15 segments of the barrier can be carried and transported as a unit. The transfer vehicle oper­ates in either direction and is operationally symmetrical. Each end of the vehicle is independently steered with its own steering wheel. Movement can be controlled from either end.

DEMONSTRATIONS OF TRANSFER VEHICLE

A prototype transfer vehicle was used for four demonstra­tions. The demonstrations consisted of (a) straightening a deflected barrier after the last crash test, (b) transporting and assembling a IO- egm nt length of barrier ( c) tran fcrring a barrier on a 1 400-ft radius with a 12 percent cros lop and (d) tran ferring a barrier on a 4 to 5 percent longitudinal grade.

The first demonstration showed the ability of the transfer vehicle to realign a deflected barrier. The barrier was deflected by Test 446 a maximum of 2.24 ft (683 mm). The barrier was back to a straight alignment in its original position after two passes (Figure 19). It appeared that with more experienced operators the barrier could have been made straight with only one pass . Realignment was accomplished without placing

Impact I+0.118 s I+ 0.238 s

I + 0.458 s I+ 0.71 s

~riha Final Position ~ aU-.JJ 0.!.~ Car Displaced f t ------~~:_th Segments __ 41 ---- r-- sr --J --+ ., ''' ·" ,, . tiio:.ri-::::-. >t;"';; ~ ;"ffej;-: r·: '",:" ~~,:_· .. ;; __ '"'---'

7'l .. .. 32s·-----------_____.:1 1'=0.3048m NOTTO SCALE

Test Barrier: Type : Movable Concrete Barrier (Simple Hinge Connections with Reduced Clearance) Length:

Test Date: TestVehlcle:

Model: Inertial Mass: Impact Velocity: Impact; Exit Angle:

Test Dummy: Type: Weight I Restraint: Position:

Test Data:

328 ft (100 m ) - 100 segments January 21, 1988

1982 Olds Station Wagon 4300 lb (1950 kg) 59.4 mph (26.6 mis) 16deg; 16112deg

Part 572, 50th Percentile Male 165 lb (75 kg)/ none Driver's seat

Occupant Impact Velocity (long): 14.3 fps (4.4 mis) Max 50 ms Avg Accel: HIC I TAD I VOi: Max Roll;Pitch;Yaw : Barrier Displacement: Max Dynamic Deflection (film) :

long -3.3 g, lat -5.9 g, vert -1. 7 g 45 I LFQ4 I 12LDEE2 6114 deg; 53/B deg; NA 2.85 ft (0.87 m) at segment 59 3.04 ft (0.93 m)

1"=0.0254m

Barrier Damage: Minor scratches and spalling at the area of contact with test car FIGURE 12 Summary of data for Test 445.

100

FIGURE 13 Car after impact, Test 445.

FIGURE 14 Deflected barrier after impact, Test 445.

workers on the ground to manually adjust the barrier. Two additional passes were made over the barrier to demonstrate simple transfer operation. All the functions of the transfer vehicle-lifting, lateral transport , and deposit of the mod­ules-were smooth and continuous, and the vehicle moved at about 6 mph (2.7 m/sec).

The second demonstration showed how lengths of barrier can be transported and reattached to a standing barrier. (Such an operation might be performed to move the lane closure zone of a progressing construction site.) A length of barrier, 10 segments , was loaded onto the conveyor of the transfer vehicle, carried to the location of the third demonstration, and reassembled (Figure 20). The transport distance was about 0.5 mi (800 m), and the travel speed on the paved road was about 10 mph (4.5 m/sec) . To reassemble the MCB, the bar­rier on the ground was aligned with the barrier within the vehicle and a hinge pin was inserted. Alignment was accom­plished by loading the portion on the ground partway into the conveyor (Figure 21) until it came in contact with the

TRANSPOR TATION RESEARCH RECORD 1258

carried barrier. There was some difficulty inserting the pin because the joint to be connected was sometimes pushed too far into the vehicle, to a place that hampered insertion. Even with that problem, though, assembly of the barrier was much faster than if it had been set one segment at a time .

The third demonstration consisted of transferring a barrier plus and minus 6 ft (1.8 m) from its original position on a curve of radius 1,400-ft (426.7 m) with a 12 percent cross slope (Figure 22). Two reference lines were laid out for use by the vehicle operators to place the barrier on each transfer run. A total of 70 segments were used to compose a barrier 230 ft (70 m) long. Two four-movement cycles were per­formed. In each cycle , the barrier was first moved outward to a 1,406-ft (428.5-m) radius, then inward two times to a radius of 1,394 ft ( 424. 9 m), then outward to its original position.

The last demonstration , tran ferring a barrier on a 5 percent longitudinal grade, was done in Lodi, California, at the BSI test site. The barrier consisted of 76 , egmcnt for a total le ngth of 250 ft (76 m) . The whole barrier wa tra n. ~ 1T d laterally back and forth 6 ft (1.8 m) each time from th middle , initial position. The speed of the transfer vehicle was about 5 mph (2.2 m/sec) both uphill and downhill. T.hl! barrier segments were freestanding in the first eight transfers and tethered in the second set of eight transfers.

Measurements of the joint displacements were taken across a set of four joints located about 50 ft (15 m) from each barrier end. The measurements were taken after each laleial iransfer. The net change in length was near zero after each complete transfer cycle. Stretching of the barrier apparently occurred during travel of the transfer vehicle uphill, and contraction occurred during downhill transfers. However, the number of transfers was too small for a definite pattern to be discerned.

The lateral transfers resulted in a gradual longitudinal movement of the barrier system downhill. Measurements of longitudinal movement were made at the downhill end of the barrier. The to!al longitudinal movement was 4J;.. in. (120 mm) after eight lateral tran fe rs. Because the length of the barrier did not change, as shown by the measurements above, the whole barrier must have moved longitudinally downhill.

To counteract this tendency, the upstream end of the barrier was tethered with a cable tensioned to 1,000 lb (450 N) at the beginning of each downhill run (Figure 23) . The same mea­surements as for the freestanding barrier were performed. The measurements indicated an apparent stretching of the barrier after each transfer cycle. The stretch was about 0.1 in. (2.5 mm) per joint . A total longitudinal movement of 3% in. (84 mm) occurred after eight lateral transfers. Because the upstream end of the barrier was tethered, the downhill creep may be explained by the stretch in the barrier noted .

Although creep appeared to be restricted hy pulling at the upstream end, it was not eliminated. A definite pattern or determination cannot be drawn from these data because the number of repetitions was limited.

Longitudinal creep has been reported in a similar barrier system installed in Paris , France ( 4). The total longitudinal movement of the French barrier 1.5 mi (2.4 km) long on a downhill grade of 1.5 to 2.0 percent was 3.3 to 6.6 ft (1 to 2 m) during the initial months of operation. The French solution to retard longitudinal creep was manual jacking of the uphill end of the barrier ystem before starting each daily barrier

Impact+ 0.015 s I+ 0.098 s I+0.1685

I+ 0.303 s I +0.515s I+ 1.208 s

1'=0.3048 m NOTTO SCALE Test Barrier: Type: Length:

Movable Concrete Barrier (Simple Hinge Connections with Reduced Clearance) 328 ft (100 m) - 100 segments

Test Date: TestVehlcle:

Model: Inertial Mass: Impact Velocity: Impact; Exit Angle:

Test Dummy: Type: Weight I Restraint: Position:

Test Data:

March 9, 1988

1984 Nissan 1890 lb (857 kg) 58.6 mph (26.2 mis) 20112 deg; 19112 deg

Part 572, 50th Percentile Male 165 lb (75 kg)/ none Driver's seat

Occupant Impact Velocity (long): 16.9 fps (5.2 mis) Max 50 ms Avg Accel: long -7.6 g, lat - 11.3 g, vert 2.8g HIC I TAD I VOi: 86 / LF04 / 11 LDEE2 Max Roll;Pitch;Yaw : - 1.5 deg; 12112 deg; NA Barrier Displacement: 2.24 ft (0.68 m) at segment 59 Max Dynamic Deflection (film): 2.41 ft (0.73 m)

1"=0.0254 m

Barrier Damage : Minor scratches on 2 segments at the area of contact with test car FIGURE IS Summary of data for Test 446.

102 TRANSPORTATION RESEARCH RECORD 1258

FIGURE 16 Car and barrier after impact, Test 446.

transfer in the downhill direction, similar to what was done in this demonstration.

MANUAL MOVEMENT

Another meth d of moving the M Bis by hand. Thi would be useful in making minor alignment adjustments either while assembl ing the barrier or after an impact. Movement by hand was done by a ingle p r ·on u ing a pry bar ft (2 m) long duri ng installation of the test barrier. BSI also demonstrated that a vehicle access 9 ft (2.8 m) can be made by one person in 3 min (5) .

CONCLUSIONS

FIGURE 17 Deflected barrier after impact, Test 446.

Based on the results of impact tests on this movable concrete barrier, the following conclusions can be drawn: Small cars can be smoothly redirected by a MCB with satisfactory occu· pant ri. k factor . The MCB is trong enough to fully c011tain a 4,500-lb (2040-kg) vehicle, triking at 60 mph (26 m/sec) and 25 degree with n structural failure and litt le debri. generation. The vehicle exit angle tends to be slightly more than 60 percent of the impact angle. The flanged top that is

TABLE 1 LATERAL DISPLACEMENT OF BARRIER

TEST# Vehicle ~ Impact Max. Permanent

Inertial Mass Speed, Angle, Severity Lat. Displacement

D, ft. m

443 4370 (1982) 59.3 (26.5) 24 85.0 (115) 3.74(1.14)

444 2000 (907) 57.7 (25.8) 15 1/2 15.9 (21.5) 1.78(0.54)

445 4300 (1950) 59.4 (26.6) 16 38.4 (50.8) 2.85(0.87)

446 1895 857 58.6 26.2 20 1/2 26.7 (36.1 2.24 0.68

TABLE 2 EQUATIONS TO PREDICT LATERAL DISPLACEMENT

Qgeffii::ieats

A B

D = A + B ln(IS) -1.62 1.21

(-0.592) (0.365)

2 D =A+ s(1/IS) ISC 0.961 0.0125

or D m merers, use

4

3

2

0 20 40 60

c

0.319

0.319

80

Applicable

IS Range

ft-ki s kJ

15-130 .993

(20-175)

1-130 .985

1-175

Equation 1

Equation 2

• test data

100

lmoact Severity (ft-kips) FIGURE 18 Plot of predictive equations and test data.

120

TABLE 3 TEST RESULTS

Test# 443 444 445 446 451 (§) 431 (Z) 262(.ID 264@) 301(Jl) 321 (1.Q)

Concrete Barrier MCB MCB MCB MCB New New Type Type Type Type

Tvoe Jersev Jersev 50 50 50 50

Car Mass, lbs 4370 2000 4300 1895 3575 1860 4960 4860 4860 4700

(kg) (1982) (907) (1950) (857) (1622) (844) (2250) (2200) (2200) (2130)

Impact Angle.deg 24 15 1/2 16 20 1 /2 45 52 25 25 27 26

Speed, mph 59 .3 57.7 59.4 58.6 40.3 27.4 59.0 64.0 68 .0 61 .0

(mis) (26.5) (25.8) (26.6) (26.2) (18.0) (12.2) (26.4) (28.6) (30.4) (27.3)

Roll, degrees -10 1/2 -14 1/2 6 1/2 -15 7 1/2 71 >90 NA 27 48

Pitch, degrees NA 10 1/4 5 3/8 12 1 /2 NA -2 NA NA NA NA

Yaw, degrees NA NA NA NA NA -12 NA NA NA NA

Maximum rise, in. 4.4 16.7 19.3 29.6 NA NA 34 36 38 66

Mal!:. 50 ms Ava[aga ~~alaralii:ia. g

Longitudinal1 8.3 -4.6 -3.3 -7.6 -11.2 -12.4 7.0 5.2 11 . 7 NA

Lateral2 -7.7 -6.7 -5.9 -11.3 -8.7 -5.5 11.6 13.0 13.8 NA

Qccuaaal lrn12act Velocilll ~lirnil lllli !Dlllil

Longitudina13 27.0 15.1 14.3 16.9 28 .6 32.9 NA NA NA NA

(8.2) (4.6) (4.4) (5.2) (8.7) (10.0)

Lateral (digital recorder) 18.0 NA 14.0 NA NA NA NA NA NA

NA

(5.5) (4.3)

Bide dQ:ii!D &icalaralii:ms. g

Longitudinal -5.6 -6 -3.9 -5 NA -15 NA NA NA NA

Lateral 7.6 -10 10.6 -13 NA -10 NA NA NA NA

1. TAC 191 recommended value: -5g (acceptable value: -10g)

2. TAC 191 recommended value: -3g (acceptable value: -Sg)

3. NCHAP Aeoort 230 1. recommended value: 30fos (9.1 mis)

TABLE4 IMP ACT AND EXIT CONDITIONS

Test Impact 60%of Exit Impact Exit Speed

number Angle, deg. Impact Angle, deg. Speed, V1 Speed, VE Change,

Angle, mph mph VrVE

deg. {mis) (mis) mph {m/sl

443 24 14 1/2 14 3/4 59.3 (26.5) 27.0 (12.1) 32.3 (14.4)

444 15 1/2 9114 10 1/4 57.7 (25.8) 45.8 (20.5) 11.9 (5.3)

445 16 9 1/2 16 1/2 59.4 (26.6) 48.0 (21.5) 11.4 (5.1)

446 20 1/2 12 1/4 19 1/2 58.6 (26.2) 47.6 (21.3) 11.0 (4.9)

FIGURE 19 Transfer vehicle straightening deflected barrier. FIGURE 20 Transfer vehicle carrying barrier.

FIGURE 21 Aligning barrier for connecting carried barrier and placed barrier.

106

FIGURE 22 Transfer vehicle on curve with 1,400-ft radius.

used to lift the barrier appears to limit the distance a vehicle climbs the face of the barrier thu limiting the roll angle of the vehicle. The M B deflects laterally under impact. T he lateral deflection of the MCB has a strong calistical relation to impact severity.

Based on the results of the demonstrations of movi11g the M B both with a transfer vehicle and by hand the following conclu ions can be drawn: The transfer vehicle can easily and smoothly move the barrier one full lane width at speed up to 6 mph (2.7 m/sec). Transporting, a sembling, and trans­ferring an MCB on a curve of radiu 1,400 ft (427 m) with a 12 percent cross lope and transferring a barrier on a 5 percent longitudinal grade can be successfully performed by the trnn ·­fer vehicle. And a barrier deflected as much as 2.24 ft (0.7 m) can be traightened by the transfer vehicle or can be pushed back into place with a pry bar by one person.

TRANSPORTA TION RESEARCH RECORD 1258

FIGURE 23 Tcnsio11iJ1g the tether cable.

ACKNOWLEDGMENTS

This federally funded research project was initinted by Cal­tran and wa · a j int effort of al trnns and BSL B I upplied a te t barrier in place and conducted demonstration f (he transfer vehicle . Caltrans conducted the crash tests, collected and analyzed data, and wrote the final research report (J).

REFERENCES

1. Vehicle Crash Tests of a Movable Concrete Barrier. California Department of Transportation, S3cr3mentc, 1989.

2. Basic Statistical Methods for Engineers and Scientists. Harper and Row, 1976.

3. J. D. Michie. N HRP Repon 230: Recommended Pmced11n•s for the Safe/)' Perfomu111ce Evalu11tio11 of Highway Appurwrances. TRB , National Research Council, Washington, D.C., 1981.

4. Report on the Movable Median Barrier Highway A-15 Bridge over the Seine River, Sennevifliers, France. Traffic Institute, North­western University, Evanston, Ill. 1987.

5. Movable Median Barrier for the Golden State Bridge. Barrier Systems, Inc., Sausalito, Calif., 1988.

6. A S11atbelt Efficacy Demonstration: A Large Angle Morlemte Speed lmp11c1 i/l/o n 011crete Median Barrier. Cali fornia Department of Tran porwtion . Sacramento. 1987.

7. Effects on a Vehicle Impacling a Concrete Safety Shape Barrier al a Low Speed and a Large Angle. California Department of · Transportation, Sacramento, 1986.

8. E. F . Nordlin, et al. Dynamic Tests of a Prestressed Concrele Median Barrier Type 50 Series XXVI. California Division of Highways, Sacramento, 1973.

9. E. F. Nordlin et al. Dynamic Tests of a Slipformed Concrete Barrier Type 5o Placed over a Lowered Existing Cable Harrier. California Department of Transportation , Sacramento, 1974.

10. Vehicular Crash Tests of a Continuous Concrete Median Barrier Without a Footing. California Department of Transportation, Sacramento. 1977.